This invention relates to the production of corrugated combined board. More particularly, it relates to the production of corrugated combined board on a single papermaking machine. Sometimes this type of board is referred to by other names, such as box board, corrugated container board, container board and combined board to name a few. Herein, this product will be referred to as corrugated combined board, or box board, but the invention is intended to be generic to the board product having a top and bottom liners, or linerboards, and an inner corrugated board, called corrugating medium in the papermaking industry, regardless of how it is labeled. Typically, this kind of board is used to ship bulky products, such as appliances and furniture.
Traditionally, corrugated combined board has been manufactured by producing each of the layers separately on different papermaking machines and then producing the composite board by bringing all of the board webs together on another machine and causing them to be adhesively bonded together. Indeed, in the papermaking industry, the inner, or corrugated, layer in box board is a commercial product which is manufactured exclusively on some papermaking machines in some mills. This "corrugating medium", as it is known in the trade, is produced in continuous sheets or webs and wound into rolls after it has been dried. The corrugations are then formed in the sheets by other machinery before the corrugating medium and top and bottom linerboards are brought together to form the box board.
Since box board is almost always comprised of three plies or layers--a top liner, a bottom liner and a corrugated inner layer, it now takes several machines to produce all of the layers as well as additional machines to corrugate the inner layer and glue the several layers together to form the composite box board. The top and bottom layers in a corrugated container board are commonly referred to as "linerboards" or sometimes "liners" in the paper trade. Even if all of the layers were somehow produced on a single papermaking machine, the production in terms of the composite box board would be reduced by one-third since each layer would have to be produced one at a time. In addition, each of the separate layers has to be dried separately which requires a considerable commitment in captial expenditure for drying apparatus as well as energy to dry the board webs.